1. Field of the Invention
The present invention relates to an eye refraction measuring apparatus which is to be used in an ophthalmic clinic and in an optician's store.
2. Related Background Art
A conventional auto refractometer which uses an optical position sensor has the advantage that refractivity in respective meridian directions can be simultaneously measured. Such an auto refractometer employs a special optical member such as an apertured mirror which is positioned so as to be conjugated with a pupil, and separates a projected light beam from a reflected light beam by using the optical member. On the other hand, a method of separation in which a member for dividing intensity of the light beam such as a half mirror is used has been disclosed, for example, in U.S. Pat. No. 4,162,828.
As the structure is complicated, optical systems in the above-mentioned conventional auto refractometer which separates the projected light beam from the reflected light beam by means of the apertured mirror or the like are difficult to miniaturize. Furthermore, as separation has to be performed on a pupil, sometimes an eye with an opaque pupil can not be measured. Though such problems can be solved by the method disclosed in U.S. Pat. No. 4,162,828, improvement of the measurable range and precision of an apparatus employing this method has a certain limit. For the light beam blurs on a detector except for emmetropia.
Generally, the distribution of refractivity is not uniform in a pupil. The above-mentioned conventional auto refractometers are not suitable to measure the eye with such a non-uniform distribution.
Further, the method employing a half mirror or the like should be improved so as to be applied to measurement of a pupil having a small diameter.